Planet XWhat this means is that a planet of Earth's mass could exist undetected if it were more than a few 100 AU away, and even a Jupiter (300 Earth mass planet) could exist at distances only slightly greater. The sun could have a companion brown dwarf or even a star if far enough away! It's a nice thought but it will be very tough to do anything about it unless we are lucky. The Pan STARRS telescope now under development in Hawaii will provide the best constraints in the forseeable future... There is no convincing evidence for Planet X but "absence of evidence is not evidence of absence". Such an object could exist provided it is sufficiently far away.
by David Jewitt
I was an astronomy buff, off and on, in my early teens (mid 1970s). The “Nemesis” hypothesis was very popular for explaining mass extinctions.
It went something like:
1. There are more binary star systems in the galaxy than single star systems.
2. The presence of a partner star to our Sun would cause a change in gravity affecting comets or larger asteroids as the two stars moved closer or farther apart.
3. Path changes in comets or large asteroids increase the possibility of collisions.
Now, this is what, 20 years before Hubble?